What are authentication-related bounces?

Authentication-related bounces result from failed verification:

SPF failures:

Sending IP not authorized in domain's SPF record. "SPF check failed" in bounce message. Fix: Update SPF record to include sending IPs.

DKIM failures:

Signature invalid or missing. "DKIM signature verification failed." Fix: Ensure proper DKIM signing and key publication.

DMARC failures:

Neither SPF nor DKIM aligned with From domain. Domain's DMARC policy specifies reject. "Message failed DMARC policy." Fix: Align authentication with sending domain.

Typical codes:

550 or 554 with authentication references. 5.7.1 (not authorized). 5.7.23, 5.7.25, 5.7.26 for DMARC specifically.

Response:

Review and fix authentication configuration. Test with authentication validators. Monitor DMARC reports.

Authentication bounces say "we cannot verify you are who you claim." Fix your identity credentials.